Re: erase() woes on std::multiset with custom Compare

[James Kanze]

On Nov 11, 10:12*am, [e-mail] wrote:

The secondary comparison of addresses and reverting to a
std::set will do the trick thanks.

I certainly don't want to invoke undefined behaviour. Surely
it's fine as I'm comparing pointers to the same base?

As Jerry pointed out, it's not undefined, just unspecified. To
the point where (theoretically), given two pointers a and b, a<b
might be true one time, and false the next time you try it. In
practice, of course, there are (or at least have been) a lot of
cases where !(a < b) && !(b < a), even though a and b point to
different objects (and a != b); such an ordering will NOT work
with std::set.

As Jerry also pointed out, the standard requires std::less to
work. Use it instead.

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